This document discusses the role of atmospheric oxygen in enabling the development of advanced technology on exoplanets. It argues that a minimum oxygen concentration of around 18% is required for sustainable combustion, which played a key role in processes like metallurgy that were essential for early civilizations on Earth. Periods when Earth's atmospheric oxygen dropped below this level would have inhibited the development of technology. Therefore, only planets capable of maintaining significant atmospheric oxygen over long timescales may be able to develop detectable technospheres. While complex life can evolve in low-oxygen environments, the emergence of advanced technology depends more strictly on the availability of oxygen at high concentrations through combustion.
This document summarizes the current understanding of the rise of oxygen in Earth's early ocean and atmosphere. It discusses:
1) Evidence that oxygen levels rose between 2.4-2.1 billion years ago in an event known as the Great Oxidation Event, as seen by the appearance of oxidized minerals in rock records.
2) Debate around whether oxygen-producing photosynthesis preceded or coincided with the GOE, and the role of buffers in consuming oxygen initially to delay its accumulation.
3) Strong evidence that oxygen levels rose again after the GOE but remained low for over a billion years, resulting in an oxygen-lean deep ocean until a second rise in oxygen 600 million years ago oxygen
The future life span of Earth’s oxygenated atmosphereSérgio Sacani
Earth’s modern atmosphere is highly oxygenated and is a remotely detectable signal of
its surface biosphere. However, the lifespan of oxygen-based biosignatures in Earth’s
atmosphere remains uncertain, particularly for the distant future. Here we use a
combined biogeochemistry and climate model to examine the likely timescale of
oxygen-rich atmospheric conditions on Earth. Using a stochastic approach, we find that
the mean future lifespan of Earth’s atmosphere, with oxygen levels more than 1% of the
present atmospheric level, is 1.08 ± 0.14 billion years (1σ). The model projects that a
deoxygenation of the atmosphere, with atmospheric O2 dropping sharply to levels
reminiscent of the Archaean Earth, will most probably be triggered before the inception
of moist greenhouse conditions in Earth’s climate system and before the extensive loss
of surface water from the atmosphere. We find that future deoxygenation is an
inevitable consequence of increasing solar fluxes, whereas its precise timing is
modulated by the exchange flux of reducing power between the mantle and the ocean–
atmosphere–crust system. Our results suggest that the planetary carbonate–silicate cycle
will tend to lead to terminally CO2-limited biospheres and rapid atmospheric
deoxygenation, emphasizing the need for robust atmospheric biosignatures applicable
to weakly oxygenated and anoxic exoplanet atmospheres and highlighting the potential
importance of atmospheric organic haze during the terminal stages of planetary
habitability.
The origin and geological history of oxygenrita martin
Oxygen third most profusely found element in the universe Commercially, oxygen can be prepared by the process of liquefaction and fractional distillation of air and through electrolysis of water
This document discusses the composition and structure of the atmosphere. It begins by defining the atmosphere and explaining its origin from early gases like hydrogen and helium. Over time, outgassing from the Earth's interior introduced other gases like water vapor, carbon dioxide and nitrogen. The major permanent gases that make up most of the atmosphere today are nitrogen, oxygen and argon. Variable gases like carbon dioxide, water vapor and ozone play important environmental roles despite small proportions. The atmosphere performs vital functions like supplying oxygen and protecting the planet from radiation. It facilitates processes like the water cycle and photosynthesis to support life.
The document discusses global environmental concerns, specifically focusing on ozone layer depletion and global warming. It provides details on:
- The process of ozone depletion caused by CFCs and other ozone depleting substances releasing chlorine and bromine atoms that destroy ozone.
- Effects of ozone layer depletion including increased UV radiation impacting human health, plants, aquatic ecosystems and air quality.
- International agreements like the Montreal Protocol to phase out ozone depleting substances.
- Greenhouse gases like carbon dioxide and methane causing global warming by trapping heat in the atmosphere.
- Potential impacts of climate change like rising sea levels and temperatures threatening food security and biodiversity.
-
This document provides information about the atmosphere and ozone layer. It begins by outlining syllabus objectives related to the ozone layer, greenhouse gases, and air pollution. It then defines the atmosphere and describes its composition. Subsequent sections explain how ozone is formed and maintained in the stratosphere, how CFCs deplete the ozone layer, and the environmental effects of ozone depletion. The document also discusses the importance of maintaining carbon dioxide levels and explains terms like the greenhouse effect.
The document summarizes several important biogeochemical cycles, including the carbon, nitrogen, and sulfur cycles. It describes how each element moves through the biosphere, lithosphere, atmosphere, and hydrosphere. The carbon cycle discusses the major carbon reservoirs of the atmosphere, terrestrial biosphere, oceans, sediments, and Earth's interior. Photosynthesis and respiration are key processes that move carbon between these reservoirs. The nitrogen cycle involves nitrogen fixation, nitrification, and denitrification to convert nitrogen between its different forms. The sulfur cycle notes that sulfur is important for proteins, enzymes, and plant/animal health.
This document summarizes the current understanding of the rise of oxygen in Earth's early ocean and atmosphere. It discusses:
1) Evidence that oxygen levels rose between 2.4-2.1 billion years ago in an event known as the Great Oxidation Event, as seen by the appearance of oxidized minerals in rock records.
2) Debate around whether oxygen-producing photosynthesis preceded or coincided with the GOE, and the role of buffers in consuming oxygen initially to delay its accumulation.
3) Strong evidence that oxygen levels rose again after the GOE but remained low for over a billion years, resulting in an oxygen-lean deep ocean until a second rise in oxygen 600 million years ago oxygen
The future life span of Earth’s oxygenated atmosphereSérgio Sacani
Earth’s modern atmosphere is highly oxygenated and is a remotely detectable signal of
its surface biosphere. However, the lifespan of oxygen-based biosignatures in Earth’s
atmosphere remains uncertain, particularly for the distant future. Here we use a
combined biogeochemistry and climate model to examine the likely timescale of
oxygen-rich atmospheric conditions on Earth. Using a stochastic approach, we find that
the mean future lifespan of Earth’s atmosphere, with oxygen levels more than 1% of the
present atmospheric level, is 1.08 ± 0.14 billion years (1σ). The model projects that a
deoxygenation of the atmosphere, with atmospheric O2 dropping sharply to levels
reminiscent of the Archaean Earth, will most probably be triggered before the inception
of moist greenhouse conditions in Earth’s climate system and before the extensive loss
of surface water from the atmosphere. We find that future deoxygenation is an
inevitable consequence of increasing solar fluxes, whereas its precise timing is
modulated by the exchange flux of reducing power between the mantle and the ocean–
atmosphere–crust system. Our results suggest that the planetary carbonate–silicate cycle
will tend to lead to terminally CO2-limited biospheres and rapid atmospheric
deoxygenation, emphasizing the need for robust atmospheric biosignatures applicable
to weakly oxygenated and anoxic exoplanet atmospheres and highlighting the potential
importance of atmospheric organic haze during the terminal stages of planetary
habitability.
The origin and geological history of oxygenrita martin
Oxygen third most profusely found element in the universe Commercially, oxygen can be prepared by the process of liquefaction and fractional distillation of air and through electrolysis of water
This document discusses the composition and structure of the atmosphere. It begins by defining the atmosphere and explaining its origin from early gases like hydrogen and helium. Over time, outgassing from the Earth's interior introduced other gases like water vapor, carbon dioxide and nitrogen. The major permanent gases that make up most of the atmosphere today are nitrogen, oxygen and argon. Variable gases like carbon dioxide, water vapor and ozone play important environmental roles despite small proportions. The atmosphere performs vital functions like supplying oxygen and protecting the planet from radiation. It facilitates processes like the water cycle and photosynthesis to support life.
The document discusses global environmental concerns, specifically focusing on ozone layer depletion and global warming. It provides details on:
- The process of ozone depletion caused by CFCs and other ozone depleting substances releasing chlorine and bromine atoms that destroy ozone.
- Effects of ozone layer depletion including increased UV radiation impacting human health, plants, aquatic ecosystems and air quality.
- International agreements like the Montreal Protocol to phase out ozone depleting substances.
- Greenhouse gases like carbon dioxide and methane causing global warming by trapping heat in the atmosphere.
- Potential impacts of climate change like rising sea levels and temperatures threatening food security and biodiversity.
-
This document provides information about the atmosphere and ozone layer. It begins by outlining syllabus objectives related to the ozone layer, greenhouse gases, and air pollution. It then defines the atmosphere and describes its composition. Subsequent sections explain how ozone is formed and maintained in the stratosphere, how CFCs deplete the ozone layer, and the environmental effects of ozone depletion. The document also discusses the importance of maintaining carbon dioxide levels and explains terms like the greenhouse effect.
The document summarizes several important biogeochemical cycles, including the carbon, nitrogen, and sulfur cycles. It describes how each element moves through the biosphere, lithosphere, atmosphere, and hydrosphere. The carbon cycle discusses the major carbon reservoirs of the atmosphere, terrestrial biosphere, oceans, sediments, and Earth's interior. Photosynthesis and respiration are key processes that move carbon between these reservoirs. The nitrogen cycle involves nitrogen fixation, nitrification, and denitrification to convert nitrogen between its different forms. The sulfur cycle notes that sulfur is important for proteins, enzymes, and plant/animal health.
The document summarizes key biogeochemical cycles - carbon, nitrogen, and phosphorus. It describes how carbon cycles between the atmosphere, organisms, oceans, and geosphere. The nitrogen cycle involves nitrogen fixation by bacteria, its use by organisms, and release back through denitrification. Unlike carbon and nitrogen, phosphorus does not have a gaseous phase and predominantly forms insoluble mineral compounds, cycling slowly between organisms and marine sediments.
The Ozone Layer: Formation and DepletionKamran Ansari
This presentation explains the Earth's atmosphere and its composition and variation of temperature and pressure in different layers of the atmosphere. It contains atmospheric circulation in troposphere and stratosphere. It explains the process of ozone formation and how its stability affects by the other chemical components which lead to the ozone depletion and ozone hole. It also contains the cosmic ray theory of ozone hole.
The document discusses the greenhouse effect and global warming. It explains how greenhouse gases like carbon dioxide and methane absorb infrared radiation, trapping heat in the lower atmosphere and maintaining the Earth's temperature. However, increased emissions of these gases are enhancing the greenhouse effect and causing global warming. If emissions are not reduced, climate change effects like rising sea levels and temperatures could severely impact ecosystems and human life. International agreements have aimed to limit carbon dioxide emissions but reducing them further is still needed to curb global warming.
This document discusses greenhouse gases, global warming, and the ozone layer. It provides information on major greenhouse gases like carbon dioxide, methane, and nitrous oxide and their contributions to global warming. It explains how greenhouse gases trap heat in the atmosphere and have increased global temperatures since the industrial revolution. The document also discusses effects of global warming like rising ocean temperatures, shrinking ice sheets, and ocean acidification. Additionally, it covers the ozone layer, the gases responsible for its depletion, and actions needed to support its recovery.
This document is an argumentative essay on global warming. It discusses the chemistry of ozone depletion and how CFCs released by factories destroy ozone molecules. It also argues that while global warming is occurring, the cause is uncertain as both human and natural factors may be contributing. The essay proposes more research is needed to better understand the issue.
Carbon cycle and global concerns on environmentRajat Nainwal
Carbon is the primary building block of life and cycles through different carbon pools in the biosphere, lithosphere, hydrosphere, and atmosphere. The global carbon cycle involves fluxes of carbon between these pools through natural processes like photosynthesis, respiration, and geological processes. However, human activities like burning fossil fuels and deforestation have significantly increased carbon dioxide levels in the atmosphere, disrupting the natural carbon cycle and causing global climate change. Rising global temperatures will lead to problems like rising sea levels, food shortages, and threats to biodiversity.
Greenhouse gases are compounds in Earth's atmosphere that absorb and emit infrared radiation, trapping heat in the lower atmosphere. The major greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. While some occur naturally, human activities like burning fossil fuels have increased their atmospheric concentrations since the industrial revolution. This occurs as these activities release carbon that was previously stored in solid form back into the atmosphere as a gas. The increased greenhouse gases are enhancing the natural greenhouse effect and contributing to global climate change.
The document discusses geological history and the carbon cycle on Earth. It makes three key points:
1) Geological history shows that Earth's atmosphere originally contained high levels of CO2 and low oxygen, but photosynthesis by plants decreased CO2 and increased oxygen over time.
2) Fossil fuels like oil are essentially stored solar energy in the form of organic matter that was deposited in sedimentary basins over geological time. Burning fossil fuels returns the CO2 to the atmosphere to be reused by plants.
3) Claims of human-caused global warming from CO2 emissions are incorrect because CO2 levels were originally much higher and are still very low in the atmosphere, and CO2 is rapidly recycled by
The document provides an introduction to the geo-chemistry of the atmosphere. It discusses the composition and structure of the atmosphere. The atmosphere is divided into major layers including the troposphere, stratosphere, mesosphere and thermosphere. It describes the major and minor components of the atmosphere, including nitrogen, oxygen, carbon dioxide, ozone and others. The document also discusses atmospheric processes like the greenhouse effect and how human activities have increased carbon dioxide levels, impacting the climate.
This document provides an overview of the lessons that will be covered in a course on chemicals in the natural environment. The 12 lessons will cover chemicals found in the atmosphere, hydrosphere, lithosphere and biosphere. It outlines the key concepts, objectives and activities for the first lesson which will introduce the four spheres and focus on the chemicals found in each.
1. Biogeochemistry is the study of the cycles of chemical elements like carbon and nitrogen through biological and geological systems over space and time. Key cycles include the carbon, nitrogen, phosphorus, and sulfur cycles.
2. These biogeochemical cycles involve the movement of elements between living and non-living components of the Earth system, including the atmosphere, lithosphere, hydrosphere, and biosphere.
3. Microbes play an important role in transforming elements between their various chemical forms and facilitating their movement between different Earth reservoirs as part of these global element cycles.
Yes hii88vhiirruuijhhh hiiiidttyhjhvv authentication uiiittghujh hui hai na ki mera pehela diya tha kyaa baat kr rahe ho jayega kya haal hai Bhai ka mahashivratri ka ab daily khata hu ki washroom me know if you are free please call me when you are free please call me when you are back ❤️❤️
1. The document discusses various types of pollution including air pollution, greenhouse effect, ozone layer depletion, and acid rain.
2. It notes that pollution can be in the form of chemical substances or energy and outlines some of the causes and effects of different pollutants.
3. Finally, it provides some recommendations for controlling pollution such as enforcing anti-pollution laws and properly disposing of materials.
Analysis of Stratospheric Tropospheric Intrusion as a Function of Potential V...Kalaivanan Murthy
The document provides a summary of a project report on assessing the vulnerability of stratospheric intrusions occurring in the United States based on topographic and meteorological characteristics. Stratospheric intrusions occur when stratospheric air masses diffuse into the troposphere, increasing ground-level ozone concentrations. The report discusses modeling such occurrences by analyzing potential vorticity in air masses and computing likelihood factors for different geographic grids in the US. It also reviews past stratospheric intrusion events and the importance of predicting future events for environmental regulation.
Ozone depletion describes a decline in stratospheric ozone levels since the 1970s, with a seasonal ozone hole forming over Antarctica each spring. The primary cause is chlorine and bromine atoms released from man-made chemicals like CFCs. In polar regions, ozone depletion is greatly enhanced by reactions on surfaces of polar stratospheric clouds that convert stable reservoir compounds into reactive radicals, catalytically destroying ozone. The Antarctic ozone hole forms each spring when sunlight drives these reactions after polar stratospheric clouds form over the winter.
The document summarizes the scientific discovery and diplomatic response to threats to the ozone layer from chlorofluorocarbons (CFCs). Scientists first identified that CFCs were destroying stratospheric ozone, and an Antarctic ozone hole provided evidence of the problem. This spurred international agreements like the Vienna Convention and Montreal Protocol to phase out CFC production. While uncertainties remained, nations and industries cooperated to protect the ozone layer through open scientific review and precautionary action. The ozone experience set a precedent for addressing global environmental challenges through an iterative process of science, diplomacy, and policy.
The problems attract worldwide attention K/a Global Environmental Problems.
The top three environmental problems are: (1) Greenhouse Effect and Global Warming (2) Depletion of Ozone and (3) Acid Rain.
This document describes a model of the carbon cycle and its modification to account for human activities like fossil fuel combustion and deforestation. The model includes five reservoirs - atmosphere, terrestrial biosphere, ocean surface, deep ocean, and soil. Differential equations describe the natural flows between reservoirs. The modified model adds a fossil fuel reservoir and changes flows to represent human impacts. Running the model for 500 years shows increases in atmospheric and soil carbon and a corresponding rise in global temperature of around 3.5 degrees Celsius due primarily to increased CO2 levels.
Lab 3 Sources of CO2 Emissions Part 1IntroductionThe natural.docxsmile790243
Lab 3: Sources of CO2 Emissions Part 1:
Introduction
The natural balance that occurs between global atmospheric cooling and warming processes provides an important contribution to the Earth’s varied climates.
Troposphere gases
Planetary albedo from clouds low in the troposphere, sulfur dioxide (SO2) from active volcanoes, snow, and ice all reflect incoming solar radiation back into space. This causes a cooling effect on climates within a geographical area.
Clouds high in the troposphere and greenhouse gases such as water vapor(H2O), carbon dioxide (CO2) , methane (CH4) , and nitrous oxide (N2O) have a warming effect.
Along with the solar activity, these cooling and warming processes help ensure that the planet’s average surface temperature is a net value that is above freezing, helping to ensure that life is possible.
Theory on CO2 Emissions
It has been hypothesized that anthropogenic effects (conditions caused by human activity) that are associated with industry, agriculture, and fossil fuel use have enhanced these warming processes by contributing greenhouse gases such as N2O, CH4, and CO2 into the troposphere. As a result, CO2 is believed to contribute the most to the atmospheric warming process.
Pollution
Pollution is a substance that produces a detrimental change in the environment because of its composition and abundance. Anthropogenic sources of CO2 fit this description because of the perception that there is evidence of a positive correlation between the increases in anthropogenic CO2 and increases in temperature. In turn, as temperatures increase, climates can change worldwide, unbalancing ecosystems across the globe.
Strategies
Strategies and prediction models can be used to decrease or eliminate the effects that are associated with a particular pollutant. First, the cause of the pollution must be identified. Then, scientists can create innovate ways to reduce or eliminate its production.
Part 2:
Earth System Research Laboratory
Click on the National Oceanic and Atmospheric Administration Earth System Research Laboratory, Global Monitoring Division Website. (Earth System Research Laboratory, n.d.). Here you will identify important sources of CO2 emission to help you complete your lab assignment.
Reference
Earth system research laboratory: Global monitoring division. (n.d.). Retrieved from the U.S. Department of Commerce, National Oceanic and Atmospheric Administration Research Web site: http://www.esrl.noaa.gov/gmd/obop//
End of Activity
...
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
More Related Content
Similar to The Oxygen Bottleneck for Technospheres
The document summarizes key biogeochemical cycles - carbon, nitrogen, and phosphorus. It describes how carbon cycles between the atmosphere, organisms, oceans, and geosphere. The nitrogen cycle involves nitrogen fixation by bacteria, its use by organisms, and release back through denitrification. Unlike carbon and nitrogen, phosphorus does not have a gaseous phase and predominantly forms insoluble mineral compounds, cycling slowly between organisms and marine sediments.
The Ozone Layer: Formation and DepletionKamran Ansari
This presentation explains the Earth's atmosphere and its composition and variation of temperature and pressure in different layers of the atmosphere. It contains atmospheric circulation in troposphere and stratosphere. It explains the process of ozone formation and how its stability affects by the other chemical components which lead to the ozone depletion and ozone hole. It also contains the cosmic ray theory of ozone hole.
The document discusses the greenhouse effect and global warming. It explains how greenhouse gases like carbon dioxide and methane absorb infrared radiation, trapping heat in the lower atmosphere and maintaining the Earth's temperature. However, increased emissions of these gases are enhancing the greenhouse effect and causing global warming. If emissions are not reduced, climate change effects like rising sea levels and temperatures could severely impact ecosystems and human life. International agreements have aimed to limit carbon dioxide emissions but reducing them further is still needed to curb global warming.
This document discusses greenhouse gases, global warming, and the ozone layer. It provides information on major greenhouse gases like carbon dioxide, methane, and nitrous oxide and their contributions to global warming. It explains how greenhouse gases trap heat in the atmosphere and have increased global temperatures since the industrial revolution. The document also discusses effects of global warming like rising ocean temperatures, shrinking ice sheets, and ocean acidification. Additionally, it covers the ozone layer, the gases responsible for its depletion, and actions needed to support its recovery.
This document is an argumentative essay on global warming. It discusses the chemistry of ozone depletion and how CFCs released by factories destroy ozone molecules. It also argues that while global warming is occurring, the cause is uncertain as both human and natural factors may be contributing. The essay proposes more research is needed to better understand the issue.
Carbon cycle and global concerns on environmentRajat Nainwal
Carbon is the primary building block of life and cycles through different carbon pools in the biosphere, lithosphere, hydrosphere, and atmosphere. The global carbon cycle involves fluxes of carbon between these pools through natural processes like photosynthesis, respiration, and geological processes. However, human activities like burning fossil fuels and deforestation have significantly increased carbon dioxide levels in the atmosphere, disrupting the natural carbon cycle and causing global climate change. Rising global temperatures will lead to problems like rising sea levels, food shortages, and threats to biodiversity.
Greenhouse gases are compounds in Earth's atmosphere that absorb and emit infrared radiation, trapping heat in the lower atmosphere. The major greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. While some occur naturally, human activities like burning fossil fuels have increased their atmospheric concentrations since the industrial revolution. This occurs as these activities release carbon that was previously stored in solid form back into the atmosphere as a gas. The increased greenhouse gases are enhancing the natural greenhouse effect and contributing to global climate change.
The document discusses geological history and the carbon cycle on Earth. It makes three key points:
1) Geological history shows that Earth's atmosphere originally contained high levels of CO2 and low oxygen, but photosynthesis by plants decreased CO2 and increased oxygen over time.
2) Fossil fuels like oil are essentially stored solar energy in the form of organic matter that was deposited in sedimentary basins over geological time. Burning fossil fuels returns the CO2 to the atmosphere to be reused by plants.
3) Claims of human-caused global warming from CO2 emissions are incorrect because CO2 levels were originally much higher and are still very low in the atmosphere, and CO2 is rapidly recycled by
The document provides an introduction to the geo-chemistry of the atmosphere. It discusses the composition and structure of the atmosphere. The atmosphere is divided into major layers including the troposphere, stratosphere, mesosphere and thermosphere. It describes the major and minor components of the atmosphere, including nitrogen, oxygen, carbon dioxide, ozone and others. The document also discusses atmospheric processes like the greenhouse effect and how human activities have increased carbon dioxide levels, impacting the climate.
This document provides an overview of the lessons that will be covered in a course on chemicals in the natural environment. The 12 lessons will cover chemicals found in the atmosphere, hydrosphere, lithosphere and biosphere. It outlines the key concepts, objectives and activities for the first lesson which will introduce the four spheres and focus on the chemicals found in each.
1. Biogeochemistry is the study of the cycles of chemical elements like carbon and nitrogen through biological and geological systems over space and time. Key cycles include the carbon, nitrogen, phosphorus, and sulfur cycles.
2. These biogeochemical cycles involve the movement of elements between living and non-living components of the Earth system, including the atmosphere, lithosphere, hydrosphere, and biosphere.
3. Microbes play an important role in transforming elements between their various chemical forms and facilitating their movement between different Earth reservoirs as part of these global element cycles.
Yes hii88vhiirruuijhhh hiiiidttyhjhvv authentication uiiittghujh hui hai na ki mera pehela diya tha kyaa baat kr rahe ho jayega kya haal hai Bhai ka mahashivratri ka ab daily khata hu ki washroom me know if you are free please call me when you are free please call me when you are back ❤️❤️
1. The document discusses various types of pollution including air pollution, greenhouse effect, ozone layer depletion, and acid rain.
2. It notes that pollution can be in the form of chemical substances or energy and outlines some of the causes and effects of different pollutants.
3. Finally, it provides some recommendations for controlling pollution such as enforcing anti-pollution laws and properly disposing of materials.
Analysis of Stratospheric Tropospheric Intrusion as a Function of Potential V...Kalaivanan Murthy
The document provides a summary of a project report on assessing the vulnerability of stratospheric intrusions occurring in the United States based on topographic and meteorological characteristics. Stratospheric intrusions occur when stratospheric air masses diffuse into the troposphere, increasing ground-level ozone concentrations. The report discusses modeling such occurrences by analyzing potential vorticity in air masses and computing likelihood factors for different geographic grids in the US. It also reviews past stratospheric intrusion events and the importance of predicting future events for environmental regulation.
Ozone depletion describes a decline in stratospheric ozone levels since the 1970s, with a seasonal ozone hole forming over Antarctica each spring. The primary cause is chlorine and bromine atoms released from man-made chemicals like CFCs. In polar regions, ozone depletion is greatly enhanced by reactions on surfaces of polar stratospheric clouds that convert stable reservoir compounds into reactive radicals, catalytically destroying ozone. The Antarctic ozone hole forms each spring when sunlight drives these reactions after polar stratospheric clouds form over the winter.
The document summarizes the scientific discovery and diplomatic response to threats to the ozone layer from chlorofluorocarbons (CFCs). Scientists first identified that CFCs were destroying stratospheric ozone, and an Antarctic ozone hole provided evidence of the problem. This spurred international agreements like the Vienna Convention and Montreal Protocol to phase out CFC production. While uncertainties remained, nations and industries cooperated to protect the ozone layer through open scientific review and precautionary action. The ozone experience set a precedent for addressing global environmental challenges through an iterative process of science, diplomacy, and policy.
The problems attract worldwide attention K/a Global Environmental Problems.
The top three environmental problems are: (1) Greenhouse Effect and Global Warming (2) Depletion of Ozone and (3) Acid Rain.
This document describes a model of the carbon cycle and its modification to account for human activities like fossil fuel combustion and deforestation. The model includes five reservoirs - atmosphere, terrestrial biosphere, ocean surface, deep ocean, and soil. Differential equations describe the natural flows between reservoirs. The modified model adds a fossil fuel reservoir and changes flows to represent human impacts. Running the model for 500 years shows increases in atmospheric and soil carbon and a corresponding rise in global temperature of around 3.5 degrees Celsius due primarily to increased CO2 levels.
Lab 3 Sources of CO2 Emissions Part 1IntroductionThe natural.docxsmile790243
Lab 3: Sources of CO2 Emissions Part 1:
Introduction
The natural balance that occurs between global atmospheric cooling and warming processes provides an important contribution to the Earth’s varied climates.
Troposphere gases
Planetary albedo from clouds low in the troposphere, sulfur dioxide (SO2) from active volcanoes, snow, and ice all reflect incoming solar radiation back into space. This causes a cooling effect on climates within a geographical area.
Clouds high in the troposphere and greenhouse gases such as water vapor(H2O), carbon dioxide (CO2) , methane (CH4) , and nitrous oxide (N2O) have a warming effect.
Along with the solar activity, these cooling and warming processes help ensure that the planet’s average surface temperature is a net value that is above freezing, helping to ensure that life is possible.
Theory on CO2 Emissions
It has been hypothesized that anthropogenic effects (conditions caused by human activity) that are associated with industry, agriculture, and fossil fuel use have enhanced these warming processes by contributing greenhouse gases such as N2O, CH4, and CO2 into the troposphere. As a result, CO2 is believed to contribute the most to the atmospheric warming process.
Pollution
Pollution is a substance that produces a detrimental change in the environment because of its composition and abundance. Anthropogenic sources of CO2 fit this description because of the perception that there is evidence of a positive correlation between the increases in anthropogenic CO2 and increases in temperature. In turn, as temperatures increase, climates can change worldwide, unbalancing ecosystems across the globe.
Strategies
Strategies and prediction models can be used to decrease or eliminate the effects that are associated with a particular pollutant. First, the cause of the pollution must be identified. Then, scientists can create innovate ways to reduce or eliminate its production.
Part 2:
Earth System Research Laboratory
Click on the National Oceanic and Atmospheric Administration Earth System Research Laboratory, Global Monitoring Division Website. (Earth System Research Laboratory, n.d.). Here you will identify important sources of CO2 emission to help you complete your lab assignment.
Reference
Earth system research laboratory: Global monitoring division. (n.d.). Retrieved from the U.S. Department of Commerce, National Oceanic and Atmospheric Administration Research Web site: http://www.esrl.noaa.gov/gmd/obop//
End of Activity
...
Similar to The Oxygen Bottleneck for Technospheres (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
Nucleophilic Addition of carbonyl compounds.pptxSSR02
Nucleophilic addition is the most important reaction of carbonyls. Not just aldehydes and ketones, but also carboxylic acid derivatives in general.
Carbonyls undergo addition reactions with a large range of nucleophiles.
Comparing the relative basicity of the nucleophile and the product is extremely helpful in determining how reversible the addition reaction is. Reactions with Grignards and hydrides are irreversible. Reactions with weak bases like halides and carboxylates generally don’t happen.
Electronic effects (inductive effects, electron donation) have a large impact on reactivity.
Large groups adjacent to the carbonyl will slow the rate of reaction.
Neutral nucleophiles can also add to carbonyls, although their additions are generally slower and more reversible. Acid catalysis is sometimes employed to increase the rate of addition.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
BREEDING METHODS FOR DISEASE RESISTANCE.pptxRASHMI M G
Plant breeding for disease resistance is a strategy to reduce crop losses caused by disease. Plants have an innate immune system that allows them to recognize pathogens and provide resistance. However, breeding for long-lasting resistance often involves combining multiple resistance genes
DERIVATION OF MODIFIED BERNOULLI EQUATION WITH VISCOUS EFFECTS AND TERMINAL V...Wasswaderrick3
In this book, we use conservation of energy techniques on a fluid element to derive the Modified Bernoulli equation of flow with viscous or friction effects. We derive the general equation of flow/ velocity and then from this we derive the Pouiselle flow equation, the transition flow equation and the turbulent flow equation. In the situations where there are no viscous effects , the equation reduces to the Bernoulli equation. From experimental results, we are able to include other terms in the Bernoulli equation. We also look at cases where pressure gradients exist. We use the Modified Bernoulli equation to derive equations of flow rate for pipes of different cross sectional areas connected together. We also extend our techniques of energy conservation to a sphere falling in a viscous medium under the effect of gravity. We demonstrate Stokes equation of terminal velocity and turbulent flow equation. We look at a way of calculating the time taken for a body to fall in a viscous medium. We also look at the general equation of terminal velocity.
The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptxMAGOTI ERNEST
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
1. The Oxygen Bottleneck for Technospheres
Amedeo Balbi1
and Adam Frank2
1Dipartimento di Fisica, Università di Roma “Tor Vergata”, I-00133
Roma, Italy.
2Department of Physics and Astronomy, University of Rochester,
Rochester, NY 14620, USA.
Abstract
On Earth, the development of technology required easy access to open air com-
bustion, which is only possible when oxygen partial pressure, P(O2), is above
18%. This suggests that only planets with significant atmospheric concentrations
will be capable of developing “advanced” technospheres and hence detectable
technosignatures.
Keywords: Astrobiology, extrasolar planets, extraterrestrial intelligence,
technosignatures
Atmospheric oxygen has played an important role in astrobiological studies. Because it
is an essential component of respiration and metabolism for multicellular organisms on
Earth, some researchers have argued that the presence of free oxygen in the atmosphere
will be essential for the evolution of complex life and intelligence on exoplanets as well
[1–3].
What has not received much attention, though, is the role of oxygen in the devel-
opment of technology on a planetary scale, or “technospheres”, of the kind that
“technosignature” studies are designed to find [4, 5]. In particular, we might ask how
does atmospheric chemistry limit or enhance the potential for a species which has
already evolved tool-using intelligence to take the next step and begin developing
higher order technological innovations. If a global scale technological civilization can-
not arise without a significant amount of atmospheric oxygen, then the limits on P(O2)
set a bottleneck for the emergence of “technospheres” on other planets.
To our knowledge, this issue has not been addressed before. The purpose of
this paper is to lay out the problem, offer some initial observations about specific
constraints, and outline the methods that may be useful in determining answers.
1
arXiv:2308.01160v1
[astro-ph.EP]
2
Aug
2023
2. 1 Oxygen regulation in the atmosphere and biology
The composition of a planet’s atmosphere depends on many factors including its astro-
nomical origins and geologic history (Figure 1). What transpired on Earth strongly
suggests that the presence of significant quantities of oxygen in the atmosphere over
long periods of time probably requires the presence of a biosphere.
The history of oxygen in Earth’s atmosphere is a complicated one (Figure 2).
Broadly speaking, O2 is primarily released by oxygenic photosynthesis, but since
organic carbon is rapidly oxidized (either by aerobic respiration or by the decay of
dead organisms), the net source of free oxygen is strongly dependent on the rate of
carbon burial through the subduction of tectonic plates in the mantle. Also impor-
tant are other processes that can deplete the atmosphere of O2, such as reactions with
reduced minerals or volcanic gases. These factors are not easy to constrain even on
modern Earth, and it is hard to predict how they might act on other planets [see 6,
for a thorough discussion]. However, it is generally believed that a substantial rise in
atmospheric oxygen and its permanence over geological times requires the evolution
of photosynthetic organisms as a necessary precondition.
The interplay between biology and atmospheric oxygen works in both directions, as
a high level of free O2 might have been a necessary precondition for the appearance of
complex life [2]. Aerobic metabolism is about ten times more energy effective than its
anaerobic counterparts for a given food intake. Also, basic chemistry suggests that no
other element can do better than oxygen as an energy source in biology. Only fluorine
and chlorine are more energetic oxidants (per electron) than oxygen, but they both
have drawbacks: they are not as abundant as oxygen in the universe, and they have
undesired side effects in organic reactions at moderate temperatures (fluorine easily
explodes, while chlorine in aqueous environment produces compounds that destroy
organic molecules). Also, both F2 and Cl2 cannot be abundant in gas form in planetary
atmospheres due to their high reactivity. Therefore, free molecular oxygen is plausibly
the most energetic source available to life in any planetary environment [note, however,
that there are counter-arguments for fluorine-based life: see, e.g., 8].
Indeed, high levels of O2 have been linked to the emergence of multicellularity [9]
and to the appearance and growth of animal life [10]. While single eukariotic cells or
small multicellular organisms are possible at oxygen concentrations as low as 0.2%, O2
levels must be at least 2% to reach the minimal size needed for basic vascularization
and circulation, ∼ 1 mm [2]. Values as high as ∼ 12% are needed for animal size
comparable to the smallest mammals existing today, ∼ 3 cm [2, 11].
Size considerations are especially important for the development of intelligent life,
requiring large and complex brains. It has also been noted [2, 12] that the use of
sophisticated technology is impossible for organisms below a minimal size. This would
create an indirect link between oxygen levels and the rise of technological species.
There is, however, a more direct connection: technology requires combustion, and
this sets strict limits on the minimal amount of free atmospheric oxygen available.
2
3. Fig. 1 Planets capable of supporting high O2 concentrations and, hence, technological
civilizations. This figure shows the likely composition of planetary atmospheres based on mass
and equilibrium temperature. For planets whose temperature and mass would lead to primarily
CO2/N2/H2O atmospheres, high oxygen levels require a biological origin, i.e. photosynthesis. For
higher equilibrium temperatures, high O2 levels can occur via the runaway greenhouse effect and the
photolysis of water vapor at high altitudes. (Figure adapted from [7].)
2 Physics and Chemistry of Combustion
On Earth, combustion can occur in open air environments because of the presence of
a fairly high oxygen partial pressure. But combustion, as a generic form of chemical
reaction, does not require such oxygen atmosphere. Combustion reactions are generally
defined as requiring a “fuel” compound and an “oxidant”. These are reacted to produce
heat and a new product. Combustion reactions often require an activation energy
barrier to be crossed (i.e. lighting a match) but once initiated they are exothermic,
with enough energy liberated to be self-sustaining, if the flux of fuel and oxidizer is
sufficient.
Typical reactions readily available on Earth are
2H2 + O2 → 2H2O + heat (1)
CH4 + 2O2 → CO2 + 2H2O + heat (2)
Note that in these reactions the oxidant is oxygen (O2 in both cases). But this
need not be the case. Combustion is an electron transfer redox reaction that moves
3
4. ATMOSPHERIC
O₂
(%)
ATMOSPHERIC
O₂
(%)
TIME (BILLIONS OF YEARS BEFORE PRESENT DAY)
TIME (MILLIONS OF YEARS BEFORE PRESENT DAY)
0
0
10
10
5
5
–4.0
–600
–3.5
–500
–3.0 –2.5
–400
–2.0
–300
–1.5
–200
–1.0 –0.5
–100
0.0
0
15
15
20
20
25
25
30
30
35
35
40
40
Global wildfires
Current O₂ level
Minimum O₂ level for combustion
Current O₂ level
Origin
of life
Appearance
of oxygen-
producing
photosynthesis
Cambrian
Explosion
Present
day
First
terrestrial
vertebrates
First animal
body plans
Fig. 2 Earth’s atmospheric O2 concentration over time. Top: O2 concentration begining at 4
Gyr ago. Bottom: O2 concentrations beginning 600 Myr ago, around the development of multicellular
life. The horizontal lines represent the current P(O2) level, the threshold for global wildfire and the
minimum requirement for combustion. In both figures we label important events in the evolution of
life. (Oxygen data from [13]. Figure adapted from [14].)
4
5. electrons (or electron density) from a less to a more “electronegative” atom. This
transfer will be both spontaneous and will release energy, which is why combustion, if
possible, may be the first energy source a young intelligent species learns to master.
While the transfer of electrons from fuel to oxidant defines combustion, the oxidant
does not have to be oxygen. Other elements and compounds can play the same role role
in combustion. Fluorine and chlorine are both possible examples of oxidants. Fluorine
combustion involves some of the most rapid and exothermic reactions known [15] and
has been proposed as an oxidizer for extreme high-performance propulsion systems.
This is due to the fact that fluorine is the most electronegative element known.
It is worth noting that combustion using oxygen as an oxidant can also occur
without the presence of significant oxygen in an atmosphere. In the modern Earth
atmosphere, fires can burn in open air because P(O2) is high enough that it is the
atmospheric oxygen molecules that serve as oxidant. But in controlled settings the
atmospheric oxygen levels can be reduced to the point where it stops being the source
of oxidant and some other compound can supply the required oxygen atoms. In these
cases the presence of an oxidizer in some form of condensed states reduces the need
for O2 from the air. Atmospheric oxygen may then still play a role in combustion but
that role is secondary [16].
3 Oxygen and technology
On Earth, fire certainly played a crucial role in the establishment of human civilization
and the onset of technology. The date for the first controlled use of fire is uncertain,
with some evidence setting it as early as 1.5 million years ago [17, 18]. There are
several ways in which the use and control of fire gave substantial advantages to our
species. Cooked food yields higher energy density compared to its raw counterpart,
and its consumption arguably produced physiological changes [larger brains, smaller
teeth and digestive apparatus; see, e.g., 19] as well as lasting social effects [20]. Fire
is also essential as a tool to change the environment: foragers may have been using it
to aid hunting and to control vegetation growth as early as 55,000 years ago [21, 22].
However, by far the most important role for fire in the rise of human civilization is
its use as an energy source. This probably started very early on as a way to keep
warm, thereby increasing the range of environmental conditions suitable for settle-
ments; then it evolved into more sophisticated uses, such as metal smelting, melding
and tool fabrication; finally, it provided both the energy source and the fuel (e.g. char-
coal) that initiated the industrial revolution and led to the “Great Acceleration” and
Anthropocene [23].
If we use the development of radio technologies as our standard of a technologically
“advanced” intelligence that might be detected across interstellar distances, then our
focus on fire (combustion) and oxygen may rest on the development of metallurgy.
All early complex civilizations on Earth relied on “worked” metals such as copper
and tin that were mass produced [24]. Copper, in particular, appears in both weapons
and tools as early as the 6th millennium BCE. Such large-scale deployment of metals
involves the application of heat in a variety of ways, the most basic of which is in
smelting, which is the process by which the metal is extracted from raw ore. The
5
6. creation of mixtures of metals, known as alloys, to enhance properties such as hardness
or resistance to corrosion, also requires the application of heat. Alloys are formed
by melting combinations of the metals together and then mixing them before they
are allowed to cool. Copper’s relatively high melting point at 1083°C meant that it
could not be purified from ores and then worked without the combustion of significant
quantities of wood or charcoal. Bronze, which played a pivotal role in the development
of premodern societies, is an alloy of copper and tin. Since tin ore contains anywhere
between 5% and 30% purity levels, the melting point required for its use ranged
between 750 and 900°C. Iron, and its alloy steel, eventually took over as the main metal
for industrial production but it required even higher melting temperature of 1535°C.
Thus the most important developments of metallurgy, i.e. the ones which led to our
ability to create an industrial base that could produce something like a radio telescope,
all relied on combustion to raise metal temperatures high enough so that phase changes
from solid to liquid could be achieved. From the first metal-working societies to the
early industrial era, this was done via the combustion of biomass. Fuel was supplied
by wood (perhaps in the form of charcoal) and the oxidizer was atmospheric oxygen.
Thus we can next enquire what atmospheric O2 levels are required for “open air”
combustion.
Experimental studies using paper as fuel have shown that the lower limit of O2
concentration for combustion in Earth’s atmosphere occurs around 16%. The proba-
bility of fire ignition, however, is strongly inhibited below 18.5%, and it is only above
a concentration of 20% that ignition can be assured [25, 26]. It is noteworthy that the
present-day oxygen concentration on Earth is 21%, which seems to sit around the sweet
spot for combustion. It has been suggested that coupled Earth system feedbacks might
help maintaining O2 around this level, as concentrations above 25% would increase
the likelihood of widespread fires ignited by lightning and quickly suppress vegetation
(and therefore photosyntesis) on the land surface, which would in turn cause a reduc-
tion in O2 [27]. Other studies have challenged this idea, showing that, depending on
moisture content, oxygen levels above 30% might still allow for the persistence of ter-
restrial plants [28]. Anyway, concentrations around 35% would likely be the highest
compatible with the existence of vegetation [29].
O2 levels are still important even when the atmospheric oxygen is not the primary
oxidizer. Experimental studies [16] found that when O2 concentration was reduced
under 18%, large variations were observed in the CO2 and CO concentrations (the reac-
tion products), suggesting that below this threshold the reactions occur only through
the oxidizer contained in the material. Thus, P(O2) ≃ 18% seems to be the limit for
both ignition and maintenance of combustion in open air atmospheric conditions.
Consideration of these findings implies that controlled use of fire on Earth (and, by
extension, the development of technology) would have been problematic during peri-
ods when P(O2) < 18%, and probably not feasible at all for P(O2) < 16%. Given the
history of oxygen concentration, the flammability of Earth could have been highly vari-
able even during the Phanerozoic, possibly switching off completely for a few tens of
million years around 180 and 200 million years ago (see Figure 2) [30]. Had a tool-using
species evolved during these periods, it would not have been able to cast metals into
6
7. the forms needed to produced “advanced” technologies like radio telescopes. General-
izing this conclusion to other planets implies the existence of comparable lower limits
to the atmospheric oxygen concentration required for the presence of a detectable
technosphere.
While we have focused on metallurgy, combustion is important for many other
processes that have contributed to development of industrial societies. The firing of
bricks for construction is a very early example of the need for combustion beyond
metallurgy. Other modern examples include the Haber process, for the production of
nitrogen based fertilizer, which optimized for production at 450°C, and the refinement
of crude oil into petroleum which requires temperatures 370°C. Space faring capabili-
ties would also be indirectly dependant on the availability of oxygen, as in the liquid
form this is the most commonly adopted oxidiser in rocket propellants.
4 Discussion and Conclusions
The main point of this article is to call attention to the fact that the oxygen concen-
tration in a planetary atmosphere required for flammability is well above the minimal
level needed to sustain a complex biosphere and multicellular organisms (Figure 2). As
combustion is an indispensable prerequisite for the onset of advanced forms of tech-
nology – such as those required for communication over interstellar distances – this
would set constraints on the kind of planetary environment capable of maintaining
a detectable technosphere. Such constraints would be far more stringent than those
required for the presence of complex life and even intelligence.
Various forms of alternative biochemistry can be conjectured for both simple life
and (to some extent) complex life [8] relying on oxidants other than oxygen to harness
chemical energy. In many cases these would, however, require unusual and problematic
atmospheric chemistry, like high fluorine concentrations (Figure 1). The development
of combustion-based technology, however, does seem to be heavily dependent on the
availability of oxygen at high concentrations.
While the build-up of an appropriate oxygen concentration seems necessary for the
development of a technological civilization, this condition is not met automatically by
the requirement that complex life is possible. Intelligent life can conceivably evolve
in an environment with low availability of free oxygen [for example in water, or in
an atmosphere with oxygen levels lower than present Earth, etc.; see 31], and ascend
to the point of developing communicating capabilities and tool utilization, but it will
eventually lack access to the large energy densities that are readily available through
combustion. Such a strong bottleneck was not taken into account in previous studies of
technosignatures. Intriguingly, the same restriction would apply even for extreme forms
of artificial or post-biological life that, although not directly dependent on oxygen,
would still need it in sufficient quantity in the atmosphere for large-scale industrial
activity to function.
The existence of an oxygen bottleneck has significant implications for future
searches of technological activities on exoplanets. Target selection might prioritize
planets with spectral O2 signatures that are above the combustion threshold and, at
the same time, the presence of high oxygen levels (or lack thereof) should serve as a
7
8. contextual prior to assess the credibility of possible evidences of technosignatures in
the data. Also, the existence of a potentially direct connection between oxygen lev-
els and technological capabilities may assist in estimating the frequency of advanced
civilizations, using theoretical models of geochemical and biological processes that
have an impact on atmospheric oxygen concentration (e.g. photosynthesis, tectonics,
global element cycles, etc.). This might give some handle on one of the unknown fac-
tors appearing in the Drake equation [32], namely fc, the fraction of planets where
intelligent life develops the technological capabilities required for interstellar commu-
nication. Should theoretical predictions show that high oxygen levels are not a likely
output of planetary evolution, this would provide a partial solution to the so called
“Fermi paradox”, or the lack of evidence for intelligent life elsewhere.
Acknowledgments. We are grateful to David Catling and Manasvi Lingam for
useful conversations.
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